The present invention concerns a device to support and mount image pickup tubes, or an integrated pickup component, and more particularly it concerns an integrated pickup component for multi-tube type color television camera and its adjusting arrangement.
There is available in the art a single tube type color television camera wherein a single image pickup tube with a color separation stripe filter is used for obtaining therefrom signals for three primary colors of the object, but it is subjected to many restrictions regarding the number of stripes of the filter and the separation of color signals, and is substantially inferior in respect of its picture quality than the multi-tube color television cameras to which reference will be made later.
The multi-tube type color television cameras, particularly tri-tube type cameras which separate the incident lights from the object by the color separation optical system into three primary colors of red (R), green (G) and blue (B), and which conduct photoelectric conversion by the respective image pickup tubes for respective colors are particularly excellent in resolution and sensitivity and reproduce excellent pictures with minimized color mixture. However, the multi-tube color television camera cannot obtain correct registration of pictures of different colors on its picture screen when the areas of separated optical images of the object which are scanned with electron beams do not coincide with each other on the target of the image pickup tube, and the picture quality becomes inferior with color blurs.
One conceivable cause for such a registration failure is the imperfect focus tracking wherein separated optical images of R, G and B do not correctly focus on the target planes of R, B and G pickup tubes. Further, even when the focus tracking is perfect and optical images of R, G, and B are correctly focused on the target plane of respective tubes, the registration mentioned above still is not obtainable if there are errors in respect of the center, the rotational position and the dimension between optical images and the electron beam scanning areas on the target planes of the corresponding image pickup tubes.
In one example of an image pickup tube device for conventional multi-tube color television camera, each image pickup tube assembly including an image pickup tube, a deflecting coil assembly arranged around the image pickup tube, a holder for holding therein the image pipckup tube and the deflecting coil assembly is securely and precisely attached to the housing of the color separation optical system of the camera, and thereafter focus tracking and adjustment for coincidence of the center position, the rotational position and dimension are effected in respect of each image pickup tube assembly.
In other words, the focus tracking worm gear attached to the holder is used to move the image pickup tube assembly in axial directions so as to make correct coincidence of the position of the target plane of the image pickup tube with the position of the object image focused by lens and color separation optical system. In order to eliminate errors in the rotational position caused by the object image inclining by a certain degree in respect of the scanning area as the corresponding sides of the rectangular electron beam scanning area and the rectangular object image are not parallel to each other, although the center positions of these rectangles are correctly registered, a rotation worm gear attached to the holder is used and the image pickup tube assembly is rotated around the tube axis. After focus tracking and rotational position are adjusted, the deflecting coil assembly is fixed tightly to the holder with an adhesive and the focus tracking worm gear and the rotation worm gear are locked. The error in center position between the electron beam scanning area and the object image, and the dimensional error which is a difference in size are usually corrected electrically by, for instance, adjusting deflection current and bias current passed through the defecting coil. Refer to NHK Technical Monograph, No. 25, March 1976, page 21, FIG. 3.6 for such a conventional device.
In the tri-tube color television camera of the prior art, components had to be assembled first, and the complicated adjustment had to be made. However, the size and weight of the camera are generally limited because smaller cameras are usually easier to handle. This leads to difficulties in adjustment arising out of the various restrictions imposed on the arrangement of the adjusting mechanism, and of the restrictions on designing camera mechanism in such small sized cameras. It was, therefore, very difficult in the prior art to manufacture inexpensive, compact, multi-tube type color television cameras. It is axiomatic that the construction becomes automatically complex if the lock mechanism has to be secured for maintaining the completed adjustment, and that the holding mechanism for this construction is requirred to be precisely frabricated from sturdy materials in order to maintain the stability of the lock mechanism.
In spite of the fact that these mechanisms become entirely unnecessary once the adjustment is completed and maintained, the conventional tri-tube type color television cameras require a highly precise and complex mechanism to make adjustment for keeping the image pickup tubes at optimum positions and angles, and a sturdy retaining mehanism to retain the adjusted precision and the superior picture quality stably. This necessarily increased the size, the weight and the cost of these cameras as well as the time required for making adjustment for the complex mehanism, thereby restricting the use of the tri-tube type color television cameras to commercial uses such as that by broadcasting stations, etc.